Snap action pressure sensitive switch with snap disc resiliently supported between legs of a terminal

ABSTRACT

A pressure-operated switch is disclosed in which one switch contact is supported by an elongated bistable snap element. The snap element is mounted on cantilever springs urging the ends of the element toward each other causing the element to bend with a single node. The spring loading is insufficient to produce multinode bending during movement of the snap element between its two positions. Several of the elements perform more than one function thereby reducing the number of elements required for the assembled device. For example, one terminal element functions to support the snap element, limit the plunger travel in one direction, and provide support for the diaphragm. Similarly, a spring functions to connect the other terminal to one contact element and to resiliently bias the plunger in one direction.

United States Patent [72} Inventors Tadeusz Budzich Moreland Hills;Frederick D. Keady, Cleveland Heights, Ohio [211 Appl. No. 858,832 [22]Filed Sept. 17, 1969 [45] Patented Apr. 6,1971 [7 3] Assignee TheWeatherhead Company Cleveland, Ohio [54] SNAP ACTION PRESSURE SENSITIVESWITCH WITH SNAP DISC RESILIENTLY SUPPORTED BETWEEN LEGS OF A TERMINAL1] Claims, 3 Drawing Figs.

[52] U.S. Cl 200/83P, 200/67DB, 200/76, 200/166CT [SI] Int. Cl H0lh35/34, H01hl3/38,I-I0lh13/48 [50] Field of Search 200/67 (D2), 76, 83.9,83, 166(ICTS), 67D (Inquired) [56] References Cited UNITED STATESPATENTS 2,040,181 5/1936 Mekelburg 200/83.9X 2,84l,66l 7/l 958 WintleZOO/76X Primary ExaminerRobert K. Schaefer Assistant ExaminerRobert A.Vanderhye Attorney- McNenny, F arrington, Pearne and Gordon ABSTRACT: Apressure-operated switch is disclosed in which one switch contact issupported by an elongated bistable snap element. The snap element ismounted on cantilever springs urging the ends of the element toward eachother causing the element to bend with a single node. The spring loadingis insufficient to produce multinode bending during movement of the snapelement between its two positions. Several of the elements perform morethan one function thereby reducing the number of elements required forthe assembled device. For example, one terminal element functions tosupport the snap element, limit the plunger travel in one direction, andprovide support for the diaphragm. Similarly, a spring functions toconnect the other terminal to one contact element and to resilientlybias the plunger in one direction.

SNAP ACTION PRESSURE SENSITIVE SWITCH WITI-I SNAP DISC RESILIEN'ILYSUPPORTED BETWEEN LEGS OF A TERMINAL BACKGROUND OF INVENTION AND PRIORART This invention relates generally to pressure-operated switchingdevices and more particularly to a pressure switch constructed andarranged to minimize the number of parts required, to reducemanufacturing and assembly costs, and to improve reliability anddurability.

The copending application of Eugene Bauniuk, Ser. No. 701,439, filedJan. 26, 1968, assigned to the assignee of the present invention,discloses a pressure-operated switch which is particularly adapted foruse in refrigeration systems or the like to prevent system operationwhen the pressure of the refrigerant is below a predetermined pressure.

A pressure-operated switch in accordance with the present invention issuitable for use in similar installations and is constructed andarranged to minimize manufacturing costs while maintaining reliabilityand durability.

SUMMARY OF INVENTION In the illustrated embodiment of this invention,the various elements of the combination are arranged so that a singleelement, in many instances,-performs a dual function in the combination.For example, a coil spring functions to bias the plunger in onedirection and also provides the electrical connection between oneterminal and the switch. A mounting ring functions to support one of theterminals, seal the diaphragm and guide the plunger assembly. Similarly,one of the terminal elements is arranged to function as a terminalconnector, a support for a snap element, and to provide a surface forthe support of the diaphragm to prevent damage thereof when thediaphragm is subjected to high pressure. With the illustrated structure,the number of parts is minimized, assembly is simplified, and the switchprovides reliability and durability.

The snap action and the differential pressure of operation of the switchis provided by a bistable element, This element is an end-loaded columnwhich is buckled into one node of a sine wave by a pair of cantileversprings which are integral parts of one terminal and act as the supportsand locators of the snap element. The column end load applied to thesnap element by the cantilever springs is sufficient to bend the snapelement into a single node, but is insuflicient to bend it into twonodes, or an S curve. With this structure greater operating accuracy isachieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevation inlongitudinal section illustrating the assembled switch device in theswitch open position;

FIG. 2 is a longitudinal section taken at right angles to the section ofFIG. 1 illustrating the switch mechanism in the switch closed position;and

FIG. 3 is a fragmentary perspective view illustrating the structure ofthe snap element and its supporting terminal.

The illustrated embodiment of this invention includes a metallic bodyelement formed with an axially extending bore 11 defining a switchcavity 12. The body is provided with an end wall 13 and a threadednipple section 14 arranged so that the switch body can be threaded intothe associated system. A flow passage 16 extends through the nipplesection and the end wall 13.

A flexible diaphragm 17 is positioned in the switch cavity 12 adjacentto the end wall 13. The diaphragm 17 is proportioned to fit within abore extension 18 in the body 10 and a central recess 19 is formed inthe body 10 adjacent to one side of the diaphragm 17 which cooperateswith the diaphragm to form a chamber 21 on one side of the diaphragmopen to the passage 16.

A mounting ring 22 formed of a nonconductive material such as a phenolicresin is positioned within the bore 11 and is axially located withrespect to the body 10 by a radial shoulder 23. The mounting ring 22 andthe body 10 are formed with annular projections 24 and 26, respectively,which press into the diaphragm surface to insure that the diaphragmseals with the body around its periphery.

The mounting ring 22 is engaged at its upper end by a closure member 27which is also formed of a nonconductive material such as a phenolicresin. The body 10 is formed with a skirt 28 which is deformed at 29overa shoulder 31 in the cap member 27 to hold the cap member 27 againstthe mounting ring 22, in turn, hold the mounting ring 22 against theshoulder 23.

A pair of terminal elements 32 and 33 extends through the closure member27 to provide external connecting portions by which the switch can beconnected to an electrical system. As best illustrated in FIG. 2, theterminal member 32 is L-shaped and is provided with a laterallyprojecting portion 34 positioned within a mating recess 36 in theclosure member 27. The upstanding portion of the terminal 32 extendsthrough an opening 37 to the exterior of the device. The closure memberis formed with a lateral shoulder 38 in the opening 37 into which alocking projection 39 extends to lock the tenninal 32 in the closuremember 27 The terminal 33 is provided with a ring portion 41 at itslower end and three upstanding projecting portions 42, 43, and 44. Theprojecting portion 44 extends upwardly through an opening 45 in theclosure member 27 to provide one of the external terminal connectionsfor the device. The other two projecting portions 42 and 43 are locatedon opposite sides of the ring portion 41 and extend up through openings46 in the mounting ring 22 as best illustrated in FIG. 1. The twoprojecting portions 42 and 43 are formed with openings 47 and adjacentV-notches 48. A metallic snap element 49 is provided with tabs 51 at itsends which extend into the openings 47 and lateral edges 52 which seatin the V-notches 48. This connection provides a simple, substantiallyfriction free mounting of the snap element 49 between the two projectingportions 42 and 43.

Located within the mounting ring 22 and guided thereby is a plungerassembly 53. The plunger assembly includes an outer cup-shaped member 54formed of a nonconductive material such as a phenolic resin, and aninner metallic cup-shaped member 56. The two members 54 and 56 areproportioned so that the cup-shaped member 56 extends down into thecupshaped member 54 with its end wall 57 engaging the end wall 58 of themember 54. The upper end of the element 56 is provided with a radialflange 59 which serves as one of the contacts of the switch mechanism.The snap element 49 is formed with a central opening 61 best illustratedin FIG. 3 through which the upper end of the plunger assembly 53projects with clearance. The snap element 49 is provided with a contact60 on each of its legs which are movable into engagement with the flange59 as illustrated in FIG. 2 to provide an electrical connectiontherebetween.

The mounting ring 22 is provided with an inwardly extending flange 62,the inner surface of which guides the plunger assembly 53. Thecup-shaped member 54 is provided with a radially extending flange 63positioned below the flange 62 and engageable therewith to limit upwardmovement of the plunger assembly. Downward movement of the plungerassembly is limited by engagement between the flange 63 and the end 64of the ring portion 41 of the terminal 33. The ring portion 41 is formedwith a conical extension 66 extending upwardly and inwardly from areverse bend at 67. The conical extension 66 is proportioned to providea smooth transition between the end wall 58 of the member 54 and thereverse bend 67 so that the diaphragm 17 is provided with smooth supportwhen the chamber 21 is pressurized to a relatively high pressure. Withthis structure, the entire diaphragm is supported against damageresulting from high pressures.

The plunger assembly 53 is urged in a downward direction toward thediaphragm 17 by a metallic coil spring 68 which extends between thelateral portion 34 of the terminal 33 and the end wall 57 of thecup-shaped member 56. The spring 68 performs a dual function of urgingthe plunger assembly 53 toward the diaphragm and also providing anelectrical connection between the cup-shaped member 56 and the terminal33.

The cup-shaped member 54 is provided with a radial surface 69 opposed toand spaced from the flange 59. The various elements are proportioned sothat movement of the plunger assembly 53 toward its upper position underthe influence of fluid under pressure in the chamber 21 causes theshoulder 69 to engage the snap member 49 and move it through itsmidposition. The snap element then snaps on through until the contact 61engages the flange 59 to close the switch. When the pressure of thefluid in the chamber 21 drops to a predetermined minimum pressure, thespring 68 causes the plunger assembly to move downwardly against theaction of the snap element and the pressure in the chamber 21 until thesnap element is carried past its midposition. When this occurs, the snapelement snaps to the position of stability illustrated in FIG. 1 and thecontact 60 snaps out of engagement with the flange S9.

The cup-shaped member 54 is preferably provided with an upstanding skirt71 proportioned to extend up through the snap member 49 even when thesnap member is in a closed position of FIG. 2. This insures thatshorting will not occur between the snap element and the cup-shapedmember 56.

The two projections 42 and 43 which support the bistable snap element 49function as cantilever springs to produce a resilient force urging theends of a snap element 49 toward each other. Therefore, the snap elementis bent with a single node toward its positions of stability. AS theplunger assembly engages the center part of the snap element it moves ittoward the midposition and the two projections 42 and 43 are deflectedoutwardly toward the phantom position illustrated in FIG. 1. Theopenings 46 are formed with clearance behind each of the projections 42and 43 to permit this deflection. Because the supporting projections 42and 43 are not rigid and can deflect outwardly as the snap element movestoward its midposition, the snap element can assume a straight conditionat its midposition and it is not necessary for the snap element toassume a compound S-type curve having two nodes. Once the snap elementpasses through its midposition, however, sufficient force is provided bythe supporting projections 42 and 43 to cause the opposite bending andthe snap element moves with snap motion to its other position ofstability. The inner walls 50 of the openings 46 engage the associatedprojections 42 and 43 to limit their inward movement and thereby limitthe amount of bending of the snap element.

Because the snap element moves between its two positions with simple,single node bending, the operating characteristics of the snap elementcan be accurately predicted by relatively simple mathematical analysis.Therefore, this structure improves the predictability of the operatingcharacteristics of the assembled device. Further, the structure, whichis symmetrical, results in a straight line movement of the contacts 60as they are carried by the snap element between its two positions ofstability. Consequently, the contacts 60 move straight into engagementwith the flange 59 without rocking movement when the switch closes.Similarly, the contacts 60 are moved away from the flange 59 with asubstantially straight line movement when the switch opens. With thisstructure, arcing is minimized and contact life is improved.

With the disclosed structure, the terminal 33 serves three functions.First, it functions as one of the terminals of the switch. Second, itsupports the snap member, and, third, it supports the diaphragm againstdamaging stress when the pressure of the fluid in the chamber reachesrelatively high pressures. The spring 68 functions to urge the plungerassembly toward the diaphragm and also functions to provide anelectrical connection between the terminal 32 and the cupshaped member56. The entire assembly is held together without separate fasteningmeans by a simple expedient of bending the skirt 28 over a mating flangeon the closure member 27.

Although a preferred embodiment of this invention is illustrated, it isto be understood that various modifications and rearrangements may beresorted to without departing from the scope of the invention disclosed.

We claim:

1. A snap switch comprising a body assembly, a plunger mounted in saidbody assembly for reciprocation between first and second positions, apair of opposed supports in said body assembly with one on each side ofsaid plunger, a resilient snap element supported at its ends on saidopposed supports and formed with a central opening through which saidplunger assembly extends, said snap element providing a leg on each sideof said plunger assembly, said supports urging the ends of said snapelement toward each other and causing said snap element to bend with asingle node so that said snap element is provided with two positions ofstability, said plunger assembly providing opposed surfaces on oppositesides of said snap element engageable with said snap elementsubstantially midway between its ends, one of said opposed surfacesbeing electrically conductive and in engagement with said snap elementwhen said snap element is in its first position of stability and saidplunger is in its first position, movement of said plunger to its secondposition causing said snap element to move through a position ofinstability and causing said snap element to move with snap motion outof contact with said conductive surface to its second position ofstability, and a pair of terminals adapted to be connected to anexternal circuit, one of said terminals being electrically connected tosaid conductive surface and the other of said terminals beingelectrically connected to said snap element.

2. A snap switch as set forth in claim 1 wherein said supportsresiliently urge the ends of said snap element toward each other withsufficient force to cause said snap element to bend with a single nodeand insufficient force to cause said snap element to bend with a doublenode.

3. A snap switch as set forth in claim 2 wherein said conductive surfaceengages both of said legs substantially midway between the two ends ofsaid snap element.

4. A snap switch as set forth in claim 3 wherein a contact element ismounted on each of said legs substantially midway between the ends ofsaid snap element.

5. A snap switch as set forth in claim 4 wherein said other terminalincludes a terminal portion exterior of said body assembly andintegrally formed cantilever spring portions providing said opposedsupports, said snap element being mounted on the free ends of saidcantilever spring portions.

6. A snap switch as set forth in claim 4 wherein contact elements arecarried by said snap element for movement into and out of engagementwith said conductive surface, said contact means moving withsubstantially straight line movement when said snap element movesbetween said first and second positions of stability.

7. A snap switch comprising a body assembly provided with a switchchamber, a pair of terminal members each having a terminal portionadapted to be connected to an external circuit, one of said terminalmembers providing opposed integrally formed cantilever spring portions,a resilient snap element mounted at its ends on the free ends of saidcantilever spring portions, said spring portions urging the ends of saidsnap element toward each other to cause the snap element to bow with asingle node and provide two positions of stability, a plunger assemblyin said body assembly reciprocable between said first and secondpositions, contact means carried by said plunger assembly electricallyconnected to the other of said terminal members and operable to engagesaid snap element to provide an electrical connection between saidterminal members, a spring operable to urge said plunger assembly towardits first position, a diaphragm mounted in said body assembly operablyconnected to said plunger assembly to overcome said spring and move saidplunger assembly to its second position, said one terminal memberproviding a support section around said plunger assembly engageable withsaid diaphragm when said diaphragm moves said plunger assembly to saidsecond position to cooperate with said plunger assembly and providesubstantially complete support of said diaphragm.

8. A snap switch asset forth in claim 7 wherein said support sectionprevents movement beyond said first position in a direction away fromsaid second position.

9. A snap switch as set forth in claim 8 wherein said spring providesthe electrical connection between said contact means and said otherterminal member.

10. A pressure responsive switching device comprising a body formed witha switch cavity having an apertured end wall, a flexible diaphragmpositioned against said end wall, a nonconductive mounting ring in saidbody pressing said diaphragm into sealing engagement with said end wall,a first terminal element mounted on said mounting ring and provided withopposed support projections, a snap-acting contact mounted at its endson said projections, a plunger assembly including a cup-shapednonconductive plunger element axially movable along said mounting ringand a cup-shaped electrically conductive plunger element telescopinginto said nonconductive plunger element, a closure element positionedagainst the end of said mounting ring pressed in a direction toward saidmounting ring by said body, a second terminal on said closure element, aconductive spring extending between said second tenninal and saidelectrically conductive plunger element operating to electricallyconnect them and to urge said plunger assembly and said diaphragm towardsaid first position, fluid under pressure admitted to one side of saiddiaphragm through said apertured end wall operating to overcome saidspring and move said plunger assembly to said second position whenpredetennined pressures exist, said plunger elements each providing aradially extending surface with one on each side of said snap-actingcontact, said radial surfaces cooperating to engage said snap-actingcontact to move it between said positions of stability when said plungermoves between said first and second positions, said snap-acting elementengaging said radial surface of said electrically conductive plungerelement when said plunger assembly is in one of said first and secondpositions to provide an electrical connection between said surfaces.

11. A pressure responsive switching device as set forth in claim 10wherein said opposed support projections are resilient cantileversprings which urge the ends of said snapacting contact toward each otherwith sufficient force to bend said snap-acting contact with a singlenode and insufi'icient force to bend it with a multinode.

1. A snap switch comprising a body assembly, a plunger mounted in saidbody assembly for reciprocation between first and second positions, apair of opposed supports in said body assembly with one on each side ofsaid plunger, a resilient snap element supported at its ends on saidopposed supports and formed with a central opening through which saidplunger assembly extends, said snap element providing a leg on each sideof said plunger assembly, said supports urging the ends of said snapelement toward each other and causing said snap element to bend with asingle node so that said snap element is provided with two positions ofstability, said plunger assembly providing opposed surfaces on oppositesides of said snap element engageable with said snap elementsubstantially midway between its ends, one of said opposed surfacesbeing electrically conductive and in engagement with said snap elementwhen said snap element is in its first position of stability and saidplunger is in its first position, movement of said plunger to its secondposition causing said snap element to move through a position ofinstability and causing said snap element to move with snap motion outof contact with said conductive surface to its second position ofstability, and a pair of terminals adapted to be connected to anexternal circuit, one of said terminals being electrically connected tosaid conductive surface and the other of said terminals beingelectrically connected to said snap element.
 2. A snap switch as setforth in claim 1 wherein said supports resiliently urge the ends of saidsnap element toward each other with sufficient force to cause said snapelement to bend with a single node and insufficient force to cause saidsnap element to bend with a double node.
 3. A snap switch as set forthin claim 2 wherein said conductive surface engages both of said legssubstantially midway between the two ends of said snap element.
 4. Asnap switch as set forth in claim 3 wherein a contact element is mountedon each of said legs suBstantially midway between the ends of said snapelement.
 5. A snap switch as set forth in claim 4 wherein said otherterminal includes a terminal portion exterior of said body assembly andintegrally formed cantilever spring portions providing said opposedsupports, said snap element being mounted on the free ends of saidcantilever spring portions.
 6. A snap switch as set forth in claim 4wherein contact elements are carried by said snap element for movementinto and out of engagement with said conductive surface, said contactmeans moving with substantially straight line movement when said snapelement moves between said first and second positions of stability.
 7. Asnap switch comprising a body assembly provided with a switch chamber, apair of terminal members each having a terminal portion adapted to beconnected to an external circuit, one of said terminal members providingopposed integrally formed cantilever spring portions, a resilient snapelement mounted at its ends on the free ends of said cantilever springportions, said spring portions urging the ends of said snap elementtoward each other to cause the snap element to bow with a single nodeand provide two positions of stability, a plunger assembly in said bodyassembly reciprocable between said first and second positions, contactmeans carried by said plunger assembly electrically connected to theother of said terminal members and operable to engage said snap elementto provide an electrical connection between said terminal members, aspring operable to urge said plunger assembly toward its first position,a diaphragm mounted in said body assembly operably connected to saidplunger assembly to overcome said spring and move said plunger assemblyto its second position, said one terminal member providing a supportsection around said plunger assembly engageable with said diaphragm whensaid diaphragm moves said plunger assembly to said second position tocooperate with said plunger assembly and provide substantially completesupport of said diaphragm.
 8. A snap switch as set forth in claim 7wherein said support section prevents movement beyond said firstposition in a direction away from said second position.
 9. A snap switchas set forth in claim 8 wherein said spring provides the electricalconnection between said contact means and said other terminal member.10. A pressure responsive switching device comprising a body formed witha switch cavity having an apertured end wall, a flexible diaphragmpositioned against said end wall, a nonconductive mounting ring in saidbody pressing said diaphragm into sealing engagement with said end wall,a first terminal element mounted on said mounting ring and provided withopposed support projections, a snap-acting contact mounted at its endson said projections, a plunger assembly including a cup-shapednonconductive plunger element axially movable along said mounting ringand a cup-shaped electrically conductive plunger element telescopinginto said nonconductive plunger element, a closure element positionedagainst the end of said mounting ring pressed in a direction toward saidmounting ring by said body, a second terminal on said closure element, aconductive spring extending between said second terminal and saidelectrically conductive plunger element operating to electricallyconnect them and to urge said plunger assembly and said diaphragm towardsaid first position, fluid under pressure admitted to one side of saiddiaphragm through said apertured end wall operating to overcome saidspring and move said plunger assembly to said second position whenpredetermined pressures exist, said plunger elements each providing aradially extending surface with one on each side of said snap-actingcontact, said radial surfaces cooperating to engage said snap-actingcontact to move it between said positions of stability when said plungermoves between said first and second positions, said snap-acting elementengaging said radial surface of said electRically conductive plungerelement when said plunger assembly is in one of said first and secondpositions to provide an electrical connection between said surfaces. 11.A pressure responsive switching device as set forth in claim 10 whereinsaid opposed support projections are resilient cantilever springs whichurge the ends of said snap-acting contact toward each other withsufficient force to bend said snap-acting contact with a single node andinsufficient force to bend it with a multinode.